I haven’t played around much with the calendar loop yet myself, but it’s interesting to see that pagination does seem to work on calendar loops to some extent even though this isn’t an official feature (yet)! It makes sense that the template in your first post wouldn’t work since in the current implementation of pagination, the
<PaginateButtons /> tag needs to be placed outside a loop and in your first example, it was placed inside. I’m not sure if it’s currently possible to loop multiple instances of pagination as you’re trying to do, so that might be where things are breaking. I know that work is underway to make the pagination options a lot more flexible so that should make this kind of thing easier to achieve.
This part does indeed seem like a bug so I’ve reported it to the dev team and I’ll report back here when it’s been resolved.